Chilesaurus diegosuarezi is the first dinosaur to be discovered in Chile. It was discovered in 2004 by a family of geologists, and was described by Novas et al (complete list of contributors above) in April of 2015.

It was found in the Tonqui Formation, an outcropping near the town of Mallín Grande, 80km West of Chile Chico.

Chilesaurus is a basal (primitive) theropod from the Tithonian age, of the Late Jurassic epoch.

The holotype of Chilesaurus measured 1.2m long, but further paratypes proved that the holotype was a juvenile, the adult measuring around 3.2m long. It was bipedal, with two short arms ending in three fingers and two claws. Its small head looks to have ended in a beak.

When first being investigated, the pelvic bone of Chilesaurus was thought to resemble that of a ornithischian. Further investigation found sauropodomorph traits: a small head, leaf-shaped teeth, stocky weight-bearing legs, and strong arms with an extendable first claw (as with basal sauropods). It also contains theropod features, such as thick arms with three fingers. Following many comparisons, Chilesaurus was eventually placed into the theropod group, as a basal member of the Tetanurae family, as it didn't quite fit in any of the other families compared.

Chilesaurus' diet was herbivorous, as evidenced by its leaf-shaped teeth and backwards-facing pubic bones to make room for a larger gut for plant digestion.

"Chilesaurus" refers to the country of Chile, where this dinosaur was discovered. "Diegosuarezi" refers to Diego Suárez, who discovered the first Chilesaurus bone. Diego was looking for interesting rocks the Andes with his parents (Manuel Suárez and Rita De La Cruz, both Chilean geologists) and sister in 2004 when he brought them what he thought was a strange rock. Manuel knew that it wasn't a rock, and looked like a fossil. Manuel got in contact with Fernando Novas and Leonrdo Salgado, which ended up in an expedition to the area, where more Chilesaurus remains were found.